Help me fix a fuel vent problem

[ScaldedDog]

88 4Runner. Doesn't look stock, but the fuel system largely is: Stock tank in stockish location (may raised 1"), stock charcoal cannister in stock location. The original vent hard line to the cannister used to clog up and create tons of pressure in the tank. I finally just replaced that hard line with fuel injection hose, and the pressure problem is solved.

Now, though, on long downhill sections (Think coming home on Chinamans or Poison Spider) I'll get a strong smell of gasoline, and gas will be running through the cannister and down it's vent hose. I suppose that isn't a surprise, since there is a direct and unobstructed path to the cannister, but I don't understand why this doesn't happen on stock (but not clogged ) hard lines, nor am I sure how to fix it. Is there a check valve in the stock vent line that prevents fluid flow? Any ideas what I could put in the vent line to accomplish the same thing? The cannister tested good a couple of months ago, but I assume it's ruined with all the gas that has run through it. I don't want to just buy a new one and ruin it, too. Ideas?

Thanks!!

Mark

 

[Seth_PDX]

4x4toyotatyler had an episode about this on his podcast. Maybe the similar problem?

 

[4x4toyotatyler]

Hey Mark! My 94 has 2 valves on the charcoal cannister, one is a check valve.

Did you happen to swap both your vent and your return lines to soft fuel lines? If you did, just double check and confirm you hooked them up correctly. There should never be liquid fuel getting to your charcoal cannister. It's designed for vapor, and all the lines are hooked up with vapor possibilities. If you're getting liquid fuel oversaturation, then you most likely just hooked your fuel return to your vent line and the vent line to your fuel return at the tank. I had the exact same thing happen when I redid my lines... looked over them 50 times and hooked up one at a time to test and make sure I did them right... still messed it up and had fuel spewing out of my charcoal cannister lol.

The good news is, let the cannister dry out in some sun for a day or 2 and you should be good.

 

[Clb]

Fuel return swapped would run constantly wouldn't it?
When I did the re swap, I don't recall a check in the tank vent port.
What happened with the tank relocation?

Ask yourself what changed...

 

[GRM]

I had this issue on my land cruiser with a custom tank.

I added a fuel vent line valve that closed with high vacuum. This way when i was going downhill and off the throttle the valve would close.

Solved my problem.

 

[ScaldedDog]

Hey Mark! My 94 has 2 valves on the charcoal cannister, one is a check valve.

Did you happen to swap both your vent and your return lines to soft fuel lines? If you did, just double check and confirm you hooked them up correctly. There should never be liquid fuel getting to your charcoal cannister. It's designed for vapor, and all the lines are hooked up with vapor possibilities. If you're getting liquid fuel oversaturation, then you most likely just hooked your fuel return to your vent line and the vent line to your fuel return at the tank. I had the exact same thing happen when I redid my lines... looked over them 50 times and hooked up one at a time to test and make sure I did them right... still messed it up and had fuel spewing out of my charcoal cannister lol.

The good news is, let the cannister dry out in some sun for a day or 2 and you should be good.

Thanks Tyler. I want to say this isn't the problem, but prudence says to check it. I can't find the photos I took of the assembly, and so will need to pull it to confirm. I do know that, with the pump assembly oriented so the fuel pump port exits to the passenger frame rail, I have the vent hooked to the most forward connection, and the return line hooked to the rearmost one. Does that sound right?

Fuel return swapped would run constantly wouldn't it?
When I did the re swap, I don't recall a check in the tank vent port.
What happened with the tank relocation?

Ask yourself what changed...

Well, I know what changed - I replaced a clogged metal line with a likely larger soft one, but I don't know why that change caused a problem

I had this issue on my land cruiser with a custom tank.

I added a fuel vent line valve that closed with high vacuum. This way when i was going downhill and off the throttle the valve would close.

Solved my problem.

Do you happen to have a link to the valve you used. Assuming I have this hooked up correctly, your solution sounds like the ticket.

Thanks guys!!

Mark

 

[4x4toyotatyler]

On top of the gas tank is the hard lines coming out of the fuel pump, and then a single hard line coming out of a separate port not associated with the fuel pump port. That separate port is the vent line. The fuel pressure line and the return line go into the fuel pump port.

 

[Clb]

Frikkin shop weasals...
The check port deal is worth a shot.
I'm interested to see what happens, when I was carb'd I used a line on the bowl vent to atmosphere, to dump the overflow stuck a fuel filter on the end to keep it clear.
Cured the stumble when nose up.
Wonder if a one way vapor check valve is available?
I dunno crapshooting here...

Pic of my , some year longbed truck tank inna shortbox truck.
I need to look at the routing.
It got brazed up later, yes its redneck

 

[GRM]

The valve is an ac delco 214-552.

If you research this thing: let me know if you find a mount for it. I’m tired of it bouncing against the firewall.

 

[ScaldedDog]

OK, I've confirmed that I have the lines hooked up correctly, as you can see in the photo (from April, so the problem existed when hooked up this way). Mine fuel pump assembly and tank looks a little different than some of yours, but you can see that the center port is the return (to the bottom of the tank), and the outside port (the frontmost when mounted in the tank, and the tank in the vehicle) is the vent which only extends about and inch and a half into the tank.

GRM, how do you have that valve plumbed? (Where do the lines go?) Is your charcoal cannister the stock late-80s Toyota one?

Mark

 

[GRM]

ScaldedDog the valve is in between the charcoal canister and the intake. The vacuum line goes to a port that was blocked off on the intake, that has vacuum at idle and none off throttle.

Canister is off an fj60. Engine is a hodgepodge from fj60/fj62. All stuffed in an fj40. I can walk through more details, but its prob not applicable beyond my Frankenstein.

If you need something before the charcoal canister, install an air fuel separator. That way if the fuel gets caught in the vent line it has a place to sit rather than being sucked up with the fuel vapor.